A method and system for improving traffic communications operation over a complex interconnected network by speeding up data packet transfers using conventional protocols such as Internet Protocol (IP). More particularly, the invention interconnects Ethernet/IP Hosts over Ethernet switches, Local Area Networks (LAN) and Wide Area Networks (WAN) by virtually enlarging the LAN until it encompasses the WAN so that dynamic self-bridging can communicate anywhere in the network.
Modern digital networks are made to operate in a multimedia environment and interconnect, upon request, a large number of users and applications through complex digital communication networks.
Accordingly, due to the variety of user""s profiles and distributed applications, the corresponding traffic is consuming more and more bandwidth, non-deterministic and requiring more connectivity. This has been causing emergence of fast packet switching techniques in which data from multimedia origin are chopped into fixed length packets (e.g., in Asynchronous Transfer Mode (ATM) type of operation) or into variable length packets (e.g., in so-called Frame Relay (FR) type of operation). These packets are then transferred upon request for communication purposes between data sources and targets via so-called high speed communication networks. One of the key requirements for high speed packet switching networks is to reduce the end to end delays.
Also, due to the increase of traffic, several types of networks have been installed which need to be interconnected together to optimize the possibilities of organizing traffic between any source host and a target host both located anywhere on different LANs. This is made possible by using so-called internetworking. An internet is a collection of heterogeneous networks using a set of networking protocols (i.e., TCP/IP, Transmission Control Protocol/Internet Protocol) developed to allow cooperating computers to share resources across the network. TCP/IP products are made by many vendors and a fairly large number of networks of all kinds use it. Accordingly, IP switching technologies may incorporate new proprietary protocols, which complicates networking operations. TCP/IP is a set of data communication protocols that are referred to as the Internet protocol (IP) suite. Because TCP and IP are the best known of the protocols, it has become common to use the term TCP/IP to refer to the whole family. TCP and IP are two of the protocols in this suite. Other protocols that are part of the Internet suite are User Datagram Protocol (UDP), Internet Control Message Protocol (ICMP), Address Resolution Protocol (ARP), Real Time Protocol (RTP), Reservation Protocol (RSvP) etc.
The Internet is a collection of heterogeneous networks using TCP/IP. The administrative responsibilities for Internet (for example, to assign IP addresses and domain names) can be within a single group or distributed among multiple groups. Networks comprising an internetwork can use either the same or different technologies.
(For more information on TCP/IP one may refer to xe2x80x9cInternet Working with TCP/IPxe2x80x9d by Douglas Comer).
For example, as represented in FIG. 1, an internetwork may include networks A and B with attached stations (S1, S2, S3) using so-called Local Area Network (LAN) technology, such as token-ring, Ethernet, FDDI etc., to communicate. While within a network C, including nodes (N interconnected by links L) communication is made possible through so-called Wide Area Network (WAN) technologies including Frame Relay (FR), X.25, Asynchronous Transfer Mode (ATM) etc.
Host stations such as S1, S2, S3 . . . can each send messages from any of them to any other station. Communication within a single network is referred to as intranetworking, and communications between stations that are attached to different networks is called internetworking. Stations within a same network can communicate directly, while internetworking communications have to go across special internetworking devices called gateways and labeled R in FIG. 1 (sometimes referred to as routers as they route data from one network to another).
As shall be discussed in the following description, the gateways or routers may, in some cases, be replaced by so-called bridges. Both have specific characteristics as they operate at different layers of protocol of the network.
As computer networks have developed, various approaches have been used in the choice of communication characteristics such as communication medium, network topology, message formats, protocols for channel access etc. Some of these approaches have been converted into Standards. A model of these Standards is known as the International Standards Organization (ISO) Open System Interconnection (OSI) model. This model specifies a hierarchy of protocol layers and defines the function of each layer in the considered network. Each layer in one station which might be a host computer or a router/bridge, carries a conversation with the corresponding layer in another station with which communication is taking place, in accordance with the protocol defining the rules of this communication. In fact, information is transferred down from layer to layer in one host or router source then through the channel medium back up the successive layers in the other host or router/bridge.
Three layers (out of seven), which have been defined by the OSI Standards iclude: the physical layer, the data link layer and the network layer. The physical layer is the lowest layer assigned to transmission of data bits over the communication channel. Design of the physical layer involves issues of electrical, mechanical or optical engineering depending on the physical medium used to build the communications channel. (IETF standardizes TCP/IP thru RFCs (Requests for comments).
The main task of the layer next to the physical layer, i.e. the data link layer, is to transform the physical layer interfacing with the channel into a communication link that appears error-free to the next above layer, i.e. the network layer. The data link layer performs such functions as structuring data into packets or frames and attaching control information numbers to the packets or frames to enable checking data validity and reinserting reconstructed packets at the right location into the data flow. There are two point-to-point types: connectionless and connection oriented.
Although the data link layer is primarily independent of the nature of the transmission medium, certain aspects of the data link layer functions are dependent on the transmission medium. This is why, in some network architectures, the data link layer is divided into two sub-layers: a local control sublayer which performs all medium-independent functions of the data link layer, and a Media Access Control (MAC) sub-layer. The MAC sub-layer determines which station should get access to the communications channel, when requests for access are in conflictual situation. The functions of the MAC sub-layer are more likely to be dependent on the transmission medium nature. Bridges may be designated to operate in the MAC sub-layer.
As the internetwork topologies become more and more complex, the number of routers or bridges used to interconnect the network (see FIG. 1) become more and more important. Consequently, the choice between router and bridge devices for performing the interconnecting function may seriously impact the whole internetwork performances, e.g., in terms of transmission time delay, as each has its own advantages and disadvantages as known by any person skilled in the art.
To enable fully understanding the concerns, we shall briefly describe some of the respective characteristics of both routers and bridges.
The basic function of a bridge is to make large interconnected networks look like a single flat LAN. Bridges act at MAC layer level and listen to all message traffic on all networks (e.g. LANs) to which it is connected and to forward each message onto the networks other than the one from which the message was heard. Bridges also maintain a database of station locations derived from the content of the messages being forwarded. After a bridge has been in operation for some time, it can associate practically every station with a particular link (i.e. path) connecting the bridge to a network (e.g. LAN).
There are two main types of bridges: Transparent Bridges and Source Route Bridges, and combinations of these.
If several networks are interconnected by bridges and form a closed loop, a message may be circulated back to the network from which it was originally transmitted, which may flood the internetworking facility and jam the traffic. To prevent the formation of such closed loop a so-called Spanning Tree algorithm has been developed to connect the bridged networks into a tree configuration containing no closed loops. The spanning tree algorithm is executed periodically by the bridges on the interconnected network to ensure that the tree structure is maintained, even if the physical configuration of the network changes. Basically the bridges execute the spanning tree algorithm by sending special messages to each other to establish the identity of a xe2x80x9crootxe2x80x9d bridge. The root bridge may be selected, for convenience, as the one with the smallest numerical identification. The algorithm determines which links of the bridges are to be active and which are to be inactive, i.e. disabled, in configuring the tree structure. One more piece of terminology is needed to understand how the algorithm operates. Each network has a xe2x80x9cdesignatedxe2x80x9d link which means that one of the links connectable to the network is designated to carry traffic toward and away from the root bridge. The basis for this decision is similar to the basis for selecting the root bridge. The designated link is the one providing the least costly (shortest) path to the root bridge, with numerical bridge identification being used as a tie-break. Once the designated links are identified, the algorithm chooses two types of links to be activated or closed: first, for each network its designated link is chosen, and second, for each bridge a link that forms the xe2x80x9cbest pathxe2x80x9d to the root bridge is chosen, i.e. a link through which the bridge received a message giving the identity of the root bridge. All other links are inactivated. Execution of the algorithm results in interconnection of the network and bridges in a tree structure, i.e. one having no closed loops.
While the basic advantage of the bridge (totally multi-protocol; i.e: transparent to layer 3) is the rapidity of message transfers, these transfers operating at data link layer (i.e. layer 2), some traffic overflow may be due to bridge transparency. For instance, this is the case with TCP/IP traffic caused by so-called Address Resolution Protocol (ARP) messages made to obtain, when required, a data link layer address from the corresponding network layer address. ARP packets can be duplicated by bridges and storm the whole internetwork up to disrupting normal traffic flow.
But as far as this invention is concerned, it should essentially be recalled that bridges are transparent to broadcast messages which may then multiply and propagate through the whole internetwork. This is particularly true when bridging to build databases based on the source MAC address that flows. When a match is not found in the database, the considered packet being processed is bridged causing waste of bandwidth.
On the other hand, a router, unlike a bridge, operates at the network layer level instead of the data link layer level, and is fundamentally meant to interconnect unlike network technologies and provide a structure address space (routing based on global address. Addressing at the network layer level, as obtained by the content of data packet address field includes a unique network identifier and a target identifier within the network.
Routers learn the topology of the network and build a routing table to represent it. Tables are established manually or thru Routing Protocols (RIP, OSPF, BGP . . . , where routers learn how to reach xe2x80x9cnetworksxe2x80x9d.
Routers make use of the destination network identifier in a message to determine an optimum path from the source network to the destination network. But as far as the present invention is concerned it should be noted that broadcasted messages shall be stopped by any reached router. Consequently, in internetworking environment, routers provide a better isolation than bridges at the expense of processor utilization, time consumption and protocol sensitivity (each protocol needs different layer 3 router).
Compromises to these kinds of situations have been proposed in the art. Some have an impact on source and/or target hosts software. Then given the fairly wide variety of hosts already in the field no simple and unique solution to the problem raised may be proposed. Other solutions, like for instance the solution recommended by U.S. Pat. No. 5,309,437, addresses extended LANS and uses so-called bridge like routers including both functions. Then, discriminating on the type of traffic either one of the functions is called for use. Unfortunately during ARP operation all normal traffic is made to suffer.
One advantage of this invention is to enable improving high speed data transfers in internetwork environment by using Internet Protocol (IP) intelligence to drive self bridging configuration of conventional routers, combine effectiveness of IP routing protocols to find paths and bridging to switched packets.
Another advantage of this invention is to enable improving high speed data transfers in internetwork environment by using IP intelligence to enable self configuring routers into bridges, dynamically, during data traffic on the specific path used for connections toward a designated target host.
A further advantage of this invention is to enable improving high speed data transfers in internetwork environment requiring only limited broadcasting to enable self-configuring routers into bridges.
Another advantage of this invention is to provide a solution for efficient self-configuring routers into bridges for paths set between source and target hosts respectively attached to different LANs.
The foregoing and other objects, features and advantages of this will be made apparent from the following more detailed particular description of a preferred embodiment of the invention as illustrated in the accompanying figures.
This invention is a method for improving high speed traffic operation in an internet environment using standardized protocols of the so-called Internet Protocol (IP) suite, by speeding up data packet transfers between a source host (S) attached to a first Local Area Network (LAN) (N1), and a target host (T) attached to a different LAN (N2), both LANs being interconnected by a router (R) establishing connections at OSI Standard network level (layer 3) through use of so-called IP table, by enabling said router self-configuring into a bridge connecting at data link level (layer 2) through use of so-called Media Access Control (MAC) sublayer table, over the path between said source and target hosts, selectively and dynamically during traffic operation, said method including:
upon first packet being to be sent, pushing said packet over said first LAN toward said router R;
upon receiving said first packet, R reading its IP table locating the next hop for the target host (T) on N2, and then:
running a conventional so-called Address Resolution Protocol (ARP) over N2 to get the identified target (T) sending back its MAC address;
storing T MAC address into an ARP table and setting an entry into a so-called transparent bridging table accordingly;
reconfiguring itself into so-called Proxy-ARP to simulate it is T; sending said first packet over N2 toward T; and; applying a conventional so-called Internet Control Message Protocol (ICMP) over N1 to get all hosts (including S) located on N1 updating their IP routing table to simulate T as being attached to N1, whereby the target T is being fictively transferred upward on network N1;
upon second packet being to be sent by S toward T, having S running an ARP protocol over N1, then:
R answering with T MAC address;
S sending said second packet to T IP address with T MAC address over N1, and R bridging.
Said method recursively extend then to more complex networks including different types of LANs and WANs up to the Internet, whereby T will be fetched by last router and brought back hop by hop to first router, with each router storing T into its table.